1. Field of the Invention
The present invention relates to a thin film magnetic head and a method of manufacturing the same, and more particularly relates to an inductive type writing thin film magnetic head and a method of manufacturing the same.
2. Description of the Related Art
Recently a surface recording density of a hard disc device has been improved, and it has been required to develop a thin film magnetic head having an improved performance accordingly. A combination type thin film magnetic head is constructed by stacking an inductive type thin film magnetic head intended for writing and a magnetoresistive type thin film magnetic head intended for reading on a substrate, and has been practically used. In general, as a reading magnetoresistive element, an element utilizing anisotropic magnetoresistive (AMR) effect has been used so far and a surface recording density of about one gigabits/inch2 has been realized. In order to increase a surface record density, there has been further developed a reproducing element utilizing a giant magnetoresistive (GMR) effect having a resistance change ratio higher than that of the normal anisotropic magnetoresistive effect by several times, and a very high surface recording density of about three gigabits/inch2 has been realized. By increasing a surface recording density in this manner, it is possible to realize a hard disc device which has a very large storage capacity not less more than ten gigabytes.
The reproducing thin film magnetic head including the above mentioned GMR element has a same structure as the reproducing thin film magnetic head having the AMR element, and the AMR element is merely replaced by the GMR element. It should be noted that in the GMR element, a reproduced output is higher than that of the AMR element by 3-5 times under a same external magnetic field. The GMR film has a multiple layer structure including several films. The film structure of the GMR changes depending upon a mechanism producing the GMR effect. There have been proposed the super-lattice GMT film, glanular film, and so on. The spin valve film will be predominant owing to its simple structure, a large resistance change under a weak magnetic field and a large scale manufacture.
As stated above, a surface recording density can be simply increased by changing the AMR element by the GMR element as long as the reproducing thin film magnetic head is concerned. A height of a magnetoresistive reproducing element, i.e. MR Height (MRH) is one of factors determining a performance of the reproducing head including a magnetoresistive reproducing element. The MR height MRH is a distance measured from an air bearing surface on which one edge of the magnetoresistive reproducing element is exposed to the other edge of the element remote from the air bearing surface. During a manufacturing process of the magnetic head, a desired MR height MRH can be obtained by controlling an amount of polishing the air bearing surface.
At the same time, the performance of the recording magnetic head is also required to be improved in accordance with the improvement of the performance of the reproducing magnetic head. In order to increase a surface recording density, it is necessary to make a track density on a magnetic record medium, a width of a write gap at the air bearing surface has to be reduced to a value within a range from several micron meters to several sub-micron meters. In order to satisfy such a requirement, the semiconductor manufacturing process has been adopted for manufacturing the thin film magnetic head.
One of factors determining the performance of the inductive type writing thin film magnetic head is a throat height (TH). This throat height TH is a distance of a pole portion measured from the air bearing surface to an edge of an insulating layer which serves to separate a thin film coil from the air bearing surface. It has been required to shorten this distance as small as possible. The reduction of this throat height is also decided by an amount of polishing the air bearing surface.
Therefore, in order to improve the performance of the combination type thin film magnetic head having the inductive type recording head and magnetoresistive reading head stacked one on the other, it is very important to make the performance of the recording head and the performance of the reading head to be balanced with each other.
FIGS. 1A-7B show successive steps of a known method of manufacturing a conventional standard thin film magnetic head. In these drawings, A represents a cross sectional view cut along a plane perpendicular to the air bearing surface and B denotes a cross sectional view of a pole portion cut along a plane parallel to the air bearing surface. FIGS. 10-12 are cross sectional and plan views showing a finally manufactured completed thin film magnetic head. It should be noted that the thin film magnetic head is of a combination type in which the inductive type writing thin film magnetic head and reproducing MR element are stacked one on the other.
First of all, as shown in FIGS. 1A-B, an alumina (Al2O3) insulating layer 2 having a thickness of about 5 xcexcm is deposited on a substance 1 made of, for instance AlTiC. Next, a first magnetic layer 3 constituting a bottom shield which protects the MR reproduction element of the reproducing head from the influence of an external magnetic field, is formed with a thickness of about 3 xcexcm.
Then, as shown in FIGS. 2A-B, after depositing an alumina insulating layer 4 of thickness 100-150 nm by sputtering, a magnetoresistive layer 5 made of a material having the magnetoresistive effect and constituting the MR reproduction element is formed with a thickness not larger than ten nano meters, and is then shaped into a given pattern by the highly precise mask alignment. Then, lead electrodes 6a, 6b are formed. Next, an alumina insulating layer 7 constituting a top shield gap layer is formed with a thickness of 100-150 nm by sputtering such that the GMR layer 5 is embedded within the insulating layers 4, 7. Furthermore, a second magnetic layer 8 made of a permalloy is formed with a thickness of about 3 xcexcm. This second magnetic layer 8 has not only the function of the upper shield layer which magnetically shields the MR reproduction element together with the above described first magnetic layer 3, but also has the function of one of poles of the writing thin film magnetic head.
Then, as illustrated in FIGS. 3A-B, on the second magnetic layer 8, is formed a write gap layer 9 made of a non-magnetic material such as alumina and having a thickness of about 200 nm. Then, a photoresist layer 10 having a large thickness of 1.0-1.5 xcexcm is formed by the electroplating, and a thin film coil 11 is formed by electroplating with a thickness of 1.5-2.0 xcexcm as shown in FIGS. 4A-B. After that, as shown in FIGS. 5A-B, a photoresist insulating layer 12 is formed such that the thin film coil 11 is supported thereby in an electrically isolated manner. During this process, a reference position TH0 of throat height zero is determined by a pattern edge of the insulating layer 12. Further, an apex angle xcex8 is determined by a height of the thin film coil 11 and a configuration of a side wall of the insulating layers 10, 12. The apex angle xcex8 can be reduced to 25-35xc2x0 by increasing a distance from the reference position TH0 of throat height zero to the outermost edge of the thin film coil 12. By reducing the apex angle xcex8, the pole portion of the writing thin film magnetic head can be formed precisely by photolithography and a width of the write track determined by a width of the pole portion can be shortened.
Next, as depicted in FIG. 6, a third magnetic layer 13 made of a magnetic material having a high saturation magnetic flux density such as a permalloy (Ni:50 wt %, Fe:50 wt %) and an iron nitride (FeN) is deposited with a thickness of about 3 xcexcm. In this manner, a top pole is formed. During this process, the second magnetic layer 8 and third magnetic layer 13 are coupled with each other at a position remote from the pole portion to constitute a back gap.
Furthermore, as depicted in FIGS. 7-B, in order to avoid a spread of an effective write track width, i.e. in order to prevent a magnetic flux from being spread at a pole during the data recording, a part of the write gap layer 9 surrounding the pole chip 13a of the third magnetic layer 13 as well as the second magnetic layer 8 are etched by means of an ion beam etching such as an ion milling to form the trim structure. After that, an overcoat layer 14 made of alumina is deposited. Finally, a side on which the GMR layer 5 and write gap layer 9 are formed is polished to form an air bearing surface (ABS) 15, while the reference position of throat height zero TH0 is used as a positional reference. During the formation of the air bearing surface 15, the GMR layer 5 is also polished to form a MR reproducing element 16. In this manner, the desired throat height TH and the MR height MRH are obtained.
FIGS. 8A-C is a plan view showing the known thin film magnetic head manufactured in the manner explained above, in this figure the overcoat layer 14 is removed and the third magnetic layer 13 and lead member LD for connecting the innermost coil winding of the thin film coil 11 to an external circuit are shown by imaginary lines, and further contours of the insulating layers 10, 12 are denoted by a solid line. FIG. 8B is a cross sectional view showing its part, and FIG. 8C is a cross sectional view illustrating the back gap portion on an enlarged scale.
Upon manufacturing the known thin film magnetic head, there is a particular problem in the precise formation of the top pole on a protrusion of the thin film coil covered with the insulating photoresist layer 12 along an inclined surface (Apex) thereof after forming the thin film coil 11. In the known manufacturing method, upon forming the third magnetic layer 13, after forming a magnetic material layer such as a permalloy on the protrusion of the thin film coil having a height of 4-6 xcexcm by plating, a photoresist layer is formed thereon with a thickness of 4-5 xcexcm and then the photoresist layer is shaped into a desired pattern by means of the photolithography. Here the photoresist layer formed on the protrusion of the thin film coil should have a thickness of at least 3 xcexcm, at a bottom portion of the inclined portion, a thickness of the photoresist layer becomes about 7-8 xcexcm.
The third magnetic layer 13 formed on the protrusion of the thin film coil having a height of about 7-8 xcexcm as well as on the flat write gap layer has to be patterned such that the pole portion of the third magnetic layer near the edge of the photoresist insulating layers 7, 12 should have a narrow width, because a track width is determined by the width of the pole portion. For instance, in order to obtain a track width of, for instance 0.5 xcexcm, a pattern width of the photoresist layer having a thickness of 7-8 xcexcm should be 0.5 xcexcm.
However, such a fine patterning for forming the pattern having a width of about 0.5 xcexcm in the thick photoresist layer having a thickness of 7-8 xcexcm is very difficult. Upon exposure in the photolithography, the pattern might be deformed due to the reflection of light and the resolution might be decreased due to a large thickness of the photoresist layer. In this manner, it is particularly difficult to perform the precise patterning for the top pole which should be narrowed for realizing the narrow record track. Particularly, when the third magnetic layer 13 is formed by the electroplating, a seed layer made of a permalloy is formed by the sputtering, and therefore the pattern is liable to be deformed by the reflection from the seed layer.
The above mentioned influence of the reflection during the photolithography is also dependent upon the apex angle xcex8. If the apex angle xcex8 is large, an amount of reflected light is increased and the deformation of the pattern becomes large. In order to reduce the apex angle xcex8, a length of the pole portion 13a of the third magnetic layer 13, i.e. a distance L0 from the throat height zero reference position TH0 to the outer edge of the thin film coil 11 is made large such as 10 xcexcm as proposed in the above mentioned Japanese Patent Application Laid-open Publication Kokai Hei 8-87717. However, when the distance L0 from the throat height zero reference position TH0 to the outer edge of the thin film coil 11 is made large, a magnetic path length L1 defined by a distance between the throat height zero reference position TH0 to the inner edge of the insulating layers 19, 12 is prolonged. This results in that NLTS (Non-Linear Transition Shift) and high frequency property of the inductive type thin film magnetic head become worse. Furthermore, when the distance L0 from the throat height zero reference position TH0 to the outer edge of the thin film coil 11 is long, a magnetic flux induced by the thin film coil 11 is transmitted to the pole portion 13a only with a low efficiency, and a recording property is deteriorated.
In order to shorten the above mentioned distance L0, a pitch of coil windings of the thin film coil 11 is made as small as possible, but since the distance L0 from the throat height zero reference position TH0 to the outer edge of the thin film coil 11 has to be long for reducing the apex angle xcex8 as explained above, the magnetic path length L1 could not be shortened.
Moreover, when the thin film coil 11 is formed by the electroplating, it is necessary to provide a step in which successive coil windings are separated from each other by removing a seed layer by the ion beam etching. In this case, in order to reduce the magnetic path length L1, when a part of the thin film coil 11 is formed at an inclined portion of the insulating layer 7, there is formed a shade by a coil winding during the ion beam etching and the seed layer could not be removed sufficiently. Therefore, the thin film coil 11 has to be formed on the flat surface of the insulating layer 7, and thus there is a limitation in a reduction of the magnetic path length L1.
As shown in FIG. 8C, in order to form the innermost coil winding of the thin film coil 11 precisely, a distance L2 between the innermost edge of the thin film coil and the back gap portion should have about 5 xcexcm. Therefore, the magnetic path length L1 could not be shortened sufficiently owing to the fact that the distance L0 from the throat height zero reference position to the outermost edge of the thin film coil 11 becomes very long.
Furthermore, there has been proposed a thin film magnetic head, in which the magnetic path length L1 is shortened by constructing the thin film coil to have a double layer structure. However, in this case, a photoresist insulating layer supporting first and second layer thin film coil halves becomes higher. Then, in order to reduce the apex angle xcex8 by decreasing an inclination angle of the side wall of the insulating layer, the distance L0 from the throat height zero reference position to the outermost edge of the thin film coil 11 might become very long, and thus the reduction in the magnetic path length L1 has a limitation.
The present invention has for its object to provide a thin film magnetic head, in which the above mentioned various problems of the conventional thin film magnetic head can be solved or mitigated, while even if the apex angle xcex8 is decreased such that the fine structure of the pole portion can be manufactured precisely, the distance L0 from the throat height zero reference position TH0 to the outer edge of the thin film coil can be shortened to improve the recording efficiency, and the magnetic path length L1 can be reduced to improve the NLTS property and high frequency property.
It is another object of the invention to provide a method of manufacturing the above mentioned thin film magnetic head having the above mentioned superior properties accurately and efficiently with a high yield.
According to the invention, a thin film magnetic head comprises:
a substrate;
a first magnetic member supported by said substrate and having a recess formed in a surface thereof, said surface being opposite to a surface on which the first magnetic member is supported by the substrate, and said recess being formed at an inner position than a throat height zero reference position;
a thin film coil a part of which is provided in said recess which is formed in the surface opposite to the surface on which the first magnetic member is supported by the substrate, said thin film coil including a plurality of coil windings;
an insulating member supporting said plurality of coil windings of the thin film coil and extending externally beyond said recess, an outer edge of the insulating member defining said throat height zero reference position;
a second magnetic member formed on a surface of said insulating member remote from the substrate and including a pole portion extending up to an air bearing surface beyond said insulating member, a width of said pole portion defining a write track width; and
a write gap layer provided at least between said first magnetic member and said second magnetic member.
In the thin film magnetic head according to the invention, said at least a part of a plurality of coil windings of the thin film coil is embedded in the recess of the first magnetic member, and the insulating member supporting the coil windings of the thin film coil in an electrically insulating manner is extended beyond the periphery of the recess up to the throat height zero reference position. Therefore, a distance L0 from the throat height zero reference position to the outer periphery of the thin film coil can be shortened without increasing an apex angle xcex8, and thus a fine structure of the pole portion of the second magnetic member can be formed precisely to realize a write track width of sub-micron order and the outer periphery of the thin film coil can be closer to the air bearing surface to improve the recording efficiency. Moreover, a magnetic path length L1 defined by a distance from the throat height zero reference position to the inner edge of the insulating member supporting the coil windings of the thin film coil in an electrically insulating manner can be also shortened, and thus the NLTS and high frequency properties can be improved.
In a preferable embodiment of the thin film magnetic head according to the invention, said first magnetic layer may be formed by forming the recess in a surface of a magnetic layer having a uniform thickness or may be formed by providing a lower pole chip on a magnetic layer having a uniform thickness at a side of the air bearing surface. Furthermore, the second magnetic member may be formed by an upper pole chip constituting a pole portion and an upper pole connected to the upper pole chip. In this case, it is preferable that a front end of the upper pole is retarded from the air bearing surface. Such a structure can prevent a side fringe due a leakage of a magnetic flux from the upper pole, and an increase in the write track width and influence to adjacent tracks can be avoided. Such effects are particularly important in a fine structure in which the write track width is sub-micron order.
The thin film coil may be a single layer structure or a double layer structure. In case of the double layer structure, an insulating layer supporting coil windings of a first layer thin film coil is formed such that its outer edge is extended up to the throat height zero reference position, and an insulating layer supporting a second layer thin film coil is formed such that it is not extended beyond the outer edge of the recess up to the air bearing surface.
Moreover, the write gap layer may be formed not only between the first magnetic member and the pole portion of the second magnetic member, but also between the first magnetic member and the insulating layer or between the insulating layer and the second magnetic layer.
According to the invention, a method of manufacturing a thin film magnetic head having at least an inductive type thin film magnetic head supported by a substrate comprises:
a step of forming a first magnetic member supported by said substrate and having a recess formed in a surface which is opposite to a surface on which the first magnetic member is supported by the substrate, said recess being formed at an inner position than a throat height zero reference position;
a step of forming a thin film coil such that a part of the thin film coil is provided in said recess which is formed in the surface opposite to the surface on which the first magnetic member is supported by the substrate;
a step of forming an insulating member supporting a plurality of coil windings of the thin film coil and extending externally beyond said recess, an outer edge of the insulating member defining said throat height zero reference position;
a step of forming a write gap layer before forming said thin film coil or after forming said insulating member such that at least a pole portion of said first magnetic member is covered with said write gap layer; and
a step of forming a second magnetic member on a surface of said insulating member remote from the substrate such that said second magnetic member includes a pole portion extending up to an air bearing surface beyond said insulating member and having a width which defines a write track width.
In the manufacturing method according to the invention, it is preferable that after forming said thin film coil, a first magnetic layer supporting the coil windings is formed such that the thin film coil is completely covered with the first magnetic layer or a part of the thin film coil is exposed, and then a second magnetic layer is formed on the first magnetic layer such that an outer edge of the second magnetic layer defines the throat height zero reference position. By constructing the insulating member by the double-layer structure including the first insulating layer mainly supporting the thin film coil and the second magnetic layer mainly defining the throat height zero reference position, the first and second magnetic layers can be formed to have most suitable configurations, and thus the thin film magnetic head having a much more fine structure can be manufactured in a much easier manner.